I might be wrong, but I think as part of being a patient at a teaching hospital (which Seattle Grace is) patients have to sign a waiver that they know that they'll be "used" as part of the teaching program.

Maybe that's why they can't sue?

Just a thought.

As for Burke being outed on his hand, that's going to come out soon, probably. And, Derek will have to take some responsibility because he cleared him for work. I don't think it will be enough of a conflict between him and Cristina that she'll back out of the relationship. I think she's grown a lot since last year. I mean, you saw how she reacted with Burke's mom. She's learning how not to be so selfish. I hope she is, anyway.

Dr. Bailey will definitely take Cristina to task. She's got to get her reputation back as the Nazi. That makes two interns she lost total control of - Izzy and Christina. She has to get her act together or her career is in jeopardy as well. How can she teach her interns if she can't even keep them under control?